Re: [PATCH v14 012/138] mm: Handle per-folio private data

[Mike Rapoport]

On Thu, Jul 15, 2021 at 04:34:58AM +0100, Matthew Wilcox (Oracle) wrote:
> Add folio_get_private() which mirrors page_private() -- ie folio private
> data is the same as page private data.  The only difference is that these
> return a void * instead of an unsigned long, which matches the majority
> of users.
> 
> Turn attach_page_private() into folio_attach_private() and reimplement
> attach_page_private() as a wrapper.  No filesystem which uses page private
> data currently supports compound pages, so we're free to define the rules.
> attach_page_private() may only be called on a head page; if you want
> to add private data to a tail page, you can call set_page_private()
> directly (and shouldn't increment the page refcount!  That should be
> done when adding private data to the head page / folio).
> 
> This saves 813 bytes of text with the distro-derived config that I'm
> testing due to removing the calls to compound_head() in get_page()
> & put_page().
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
> Reviewed-by: Christoph Hellwig <hch@xxxxxx>
> Acked-by: Jeff Layton <jlayton@xxxxxxxxxx>
> Acked-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
> Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
> Reviewed-by: William Kucharski <william.kucharski@xxxxxxxxxx>
> Reviewed-by: David Howells <dhowells@xxxxxxxxxx>
> ---
>  include/linux/mm_types.h | 11 +++++++++
>  include/linux/pagemap.h  | 48 ++++++++++++++++++++++++----------------
>  2 files changed, 40 insertions(+), 19 deletions(-)

Acked-by: Mike Rapoport <rppt@xxxxxxxxxxxxx>